Dual thrust propeller and controls for rotary winged aircraft



H. J. BRYAN Jan. 19,1965

DUAL THRUST PROPELLER AND CONTROLS FOR ROTARY WINGED AIRCRAFT Filed Feb. 27. 1961 3 Sheets-Sheet 1 FIG. 1

INVENTOR.

FIG,2

H. J. BRYAN Jan. 19, 1965 DUAL THRUST PROPELLER AND CONTROLS FOR ROTARY WINGED AIRCRAFT Filed Feb. 27, 1961 3 Sheets-Sheet 2 IN VEN TOR. 2g 7 H. J. BRYAN Jan. 19, 1965 DUAL THRUST PROPELLER AND CONTROLS FOR ROTARY WINGED AIRCRAFT 3 Sheets-Sheet 3 Filed Feb. 27, 1961 a mu HW LLH $5,511,). "31;.-- 4 I g I H H IN V EN TOR. W%. @7440 3,166,129 Patented Jan. 19, 196

United States Patent .3166,l2 DUAL THRUST PROPllLLER AND CONTROLS FOR ROTARYWINGED AIRCRAFT Harvard J. Bryan, 9303 donentmDallas 28, Tex. Filed Feb. 27, 19511, Ser. No. 93,830

1 Claim. (Cl. 170-16025) This invention relates toirotary winged aircraft and trol mechanism is employed. Push-pull rods connect the rotatable portion of the fin control mechanism to bellcranks in the rotor hub. When the fin control mechanism is held in a neutral position, there is no movement of the thrust fins relative to the rotor blades. If, however, the fin control mechanism is, actuated for fin cyclic feather, a tilted plane of rotation relative to the axis of rotation ofthe rotor blades is created, causing the push-pull rods of rotation.

pull action perpendicular to the axis of rotation of the copters when cyclic pitch is employed.

rotor blades by bell eranks in the rotor hub; and by linkageto the fins, cyclic feather of the fins is accomplished,

creating thrust perpendicular to the axis of rotation of the rotor blades in any selected direction, thus providing horizontal thrust and directional control.

When .ve'rti'c al lift, or hover, is desired with no horizontalfiight, 'said :fins may be kept in neutral positions with Zero angles of attack as they rotate, or they may be collectively controlled so that they are all positioned to force air inwardly toward the axis of rotation of the rotor blades thereby increasing lift by providing a ducting effect of the rotor blades and restricting dispersal: of air,

thus increasing the volume of air which is forced downward'by the rotor blades. 'Said fins may be all positioned to force air outwardly away from the axis of rotation of the rotor blades thereby dispersing the air. and decreasing lift by decreasing the volume of-air Whichisforced downward by the' 'rotor blades permitting descent of the aircraft without changing rotor blade collective pitch or decreasing power. V Heretofore, none of the inventions relating to flying apparatus employing fins mounted'on 'members extending radially from the axis of rotation have-employed both cyclic and collective control of the angles of incidence should be understood herethat. the plane. of -rotai'tion of the rotor blades of, this invention does not tilt to produce horizontallmovement as inthe helicoptersthat employ cyclic pitch of, the rotor blades forlhoriziontal thrust. ."Ihis'fact permits the use .of said "disc.onthis 70 I helicoptersemployingicyclic pitch of the rotor blades be invention but makes it impractical to use sucha disc on cause the discwhen tilted causesprohibitive drag.

accurate movement diflicul't. Other objects? and afuller understanding of tioninay be had by referring to the. following descnptio n and. claims, taken in conjunctionwith thefaccompanying f a is to'specifically occupy an equivalent to the area occupied t by the inefficient inward-end portionof the rotor blades of;helicopters as now-cornmonl'y-known.

' 3 A further object of to. have rotor blades fully articulated.

the aircraft ,atj low jinplace. w The commonly 'fknjown helicopter fmaiieuve'rs, horizontally by actuating cyclic pitch of'the'lift' rotor lad es,

thus unbalancing lift to induce movernent' This causes *FIGURE- 3 is 7 An object of this invention is to provide an improved rotor and control system for rotary winged aircraft'that has goodau'torotation characteristics, that eliminatesthe need for lift rotor cyclic pitc'h,.and is inherently free of lift rotor cyclic pitch. helicopters and control system for rotary winged aircraft that .does not of necessity have rotor bladesfullyarticulated and thereby eliminates the use'of expensiveparts necessary A further object ofthis invention is .to provide a and control system that will have better. productibility and maintenance characteristics than conventional j heli-1 copter rotor and control systemsj n I A further object of this invention is to provide a rotor.

and control system that will more favorably jaccomrnothat type of power should be ch'osenjand this. is possible because thev absence of: cyclic pitch initherotor blades of this invention allows blade, outer tips -torotatexsubstantiall y in a'co'mmon plane man regimes of flight, con; trary to-the exaggerated upand down rotational path ofheliblade outer tips of similarly powered conventional A further object of this invention is to provide a rotor and control system for rotary winged aircraftdnherently capable of greater speed and greater lift per horsepower than is possible with helicopters tha't' d'o not e ploy ver-T tically'disposed 'fins onthe rotor blades. I l v Afeature of this invention is that this basic rotor and control' system canbe designed to accomodate' any de sired number-of rotor blades and thrust fins. t Another feature of this invention is :thatrotor blade. life will be longer due to the absenceof rotor bIadecyclic pitch and the flexing that cyclic pitch vcauses.

Another feature of this invention is thatrotor' blades may be folded downward for mooring, removal, or attaching}, i v Only thelfrotor and controls system and the new mechanisms and principles as taught in this application are claimed as nelv'v'.j It shouldlbe understood that an J craffconfiguration employing two rotors of this type is. betterfffor high'speed flight and that the aircraft body V configuration shownis for illustration purposes only and is "not "claimed asfnew. Single rotored aircraft configura-- tionsiemploying this rotor and controls system' are better for operations requiring extremely accurate control of aircraft ,to' swing frofn'flrotors like. a pendulum, making drawings in which:

1 is a plan view of the rotorlsys tem showing fins on the rotor blades cyclicly'ia'ctuated to. create thrust approximately 'infthe direction indicated by straight arrow, and, in broken lines, portions of the rotor bladeisjand F fins l 'are shown rotated forty-five idegrees counter :cloclnWise. 1' Q j Y aTper'spec tive view of atypical rotary FIGURE :2 is winged aircraft showingfthe-pr'esently preferred rotor sys; tern with thrust fins onif'otbr blades shown in neutra Positions. 'f a perspective exploded view of the rotors? vibration; which is ,nndesirable in 1 this invention is, to 'providea rotor rotor l peedssuch as set-ting churcheteeples nisrn is shownfoldeddownward," a

a 7 t and controls, in part fragmentary, with the major components separated froni each other and with portions broken away to show inside details; 7 I FIGURE 4 isa partial-plan view; of rotor blade and fin controls the rotor hub;

FIGURE Skisga partialelevationalTview looking faft,

and inbrokenlines, a rotor blade and'iits locking ineehar IGURE, 6 is a fragmentary view of the cyclic control "universal assembly the cyclic. control plate assembly.

- s,16e,129. H

R t HQ Z IFIGU E I F; PS' 1. r which there are identicalifinsabove and below the rotor blades 13, are pivota'lly attached to said rotor blade 13 and are-shown actuatedto change'their angles of injcideuce in acyclic manner during rotation'of the rotor to createthrust appronimatelyin thedirection indicated by v the straight arrow labeledkDirection of "Flight? Di- "rectio'r'r of flight is given-as approximate 'becaus' teven though the immediate results 1of actuation. for cyclic feather of said fins would creates thrustin the direction the fin fore and aft cyclic feather torque tube 29 FIG- UREf3)t0 bring about torquing of said torque tubes either separately or simultaneously as desired by the pilot to effect directional control and horizontal thrust'of the aircraft.

Lower tor ueQshaft I Z'Z "turnsv in either direction as effected by pilotsdirectional control stick, and through j a upper torque tube .31 and bevel gears" (not shown) in.

gear housing 33; torque isltransmitted'to the jack'rscrew assembly 35; Said jack iscrew assembly. is connected by rod 37, to thecyclic plate assembly, indicated in gen;

eral by numeral 391(FIGURE' 3), and pushes or pulls the cyclic plateassembly jof f center relative to'the rotor shaft 41, effecting lateralj cyclic feather control of said rotor fins -11 through linkage as will "be explained in a" later paragraph. 7

The fin lateral cyclic feather control incorporates an azimuth compensating mechanism that keeps j saidj jack" screw, assembly'35 at the same relative elevation as'cyclic 120 indicated by arrow,thedirection of thrustiand-hence direction of flightfrelative to the fin cyclic feather setting I 7 rwouldvary with varying horizontal speed due chiefly to drag increase on rotor blades and fins advancing-in" the direction of flight. During horizontal flight; said rotor blades 13 rotateinftheidirectionindicated by the curved arrow, and said fins. llproyide horizontal thrust, by V forcingair to -move a direction Opposite to thes'el'ected" a direction of flight. Said rotorffinsll; progressively] change anglefof incidence from-the greatest selected angle outward frorn :the rotor hub, indicated in general by nlumerallSQ when said rotor finsill are forward of saidrotor hub 15 approximately in the direction of flight of saidrotor'hub 15, to thegreatest selected angle of incidenceinward toward said rotor hub when, said'rotor fins fare rearward from said rotor hub and approxi I Froin the Y greatest selected 'angle of incidence inward, said rotor' mately opposite to. the..-'direetion of'flight.

finsl l then progressively reverrt 'to g the greatest selected angle of incidence outward from the rotor hub as" they return to a'position japproximatelyin the direction of flightcof the rotor hub, The fins 11" are in neutral positions'andjhave zero angles of attack when the rotor bladesa to which they are attached are at approximate right angles to the line of flightfl For creating thrust-in the direction or flight as illustrated in FIGURE 1, intbroken lines at A; a rotor is shown in the quadrant ofgthe rotational pathwhere said this 11 progressively increase angle of 'in' cidence outwardly; in .broken lines a at B Y a rotor fin r is 7 shown in the quadrant of the rotational' 'path where the.

fins progressively decrease outwardangle of incidence in t returning to neutral; In broken lines at C a rotor fin is shown inthequadrant of the rotation alfpatli where said? fins progressively increase angle of incidence inwardly r and in brokenlines at D a rotor fin is shown inrthe I quadrzintQof the'rotational path" where" said fins 11 prosplate assembly 39 at allltijrnes; thus preventing lateral cyclic effects'when fin COllfiCtlVGIGQthfilijiS changed; (Fin collectivefeather will be described in a later paragraph) c The azimuth compensating lever-43wis actuated by red 45,

' when fin collective feather is changed; becauseiof a fined "relationship of rod 45to"fincollectivepush-pull rod 47, at

their lower ends; Said lever 43 pivotsab'out thecenter line ofbolt-49, that attaches said; lever to thebody 'struc-F] ture, and raises or lowers said 'g'ear housing 33. andsaid J" jack screw assembly 35'through'connection to gear housing 33'by links 51. r a

r The up and down movement of said jack screw assembly 35 is keptp'arallelito rotor shaft '41'by1blocks 53 on studs which a are integral with gear housing 33. Said blocks 53 'slideably fit into slots of. 'stationarybrackets.

' (shown in broken lines') which are attached to the fuselage structure. A, splined jcint linking said. upper and lower torque shafts allows 'upper torque shaft 31' to move cup and down with jackscrew assembly 35 while lower torque shaft 277 remainsjstationary.

Through beve r (no W JJi l 81 3. hou

55, torque from rod 29-is transmitted to" the jack screw assembly" 57. The jackscrew beam '59 is linkedtoi'said I cyclic plate assembly39 by the rods 6lwhichare'articulatelyfattached to said beam and to said "cyclieplate assembly (FIGURE 3), andrtpushes or pulls said cyclic plate assembly off-center relative to said shaft 41, cf-

a fecting reig ite aft cyclic feather control of said rotor fins 11 through linkage as willibe explained in a later paragraph Though the absence of azimuth conipen'satinglinkagei such a s that employed inthe lateral cyclic feather control gressively decrease inward angleo'f incidence in returning torrential. At the center of said '15 an access cap lfi a is shown and'on said rotor 'bla'des" 13, between saidflfinsf 11 ancl ,:-said f'rotor blades, -fa'irings }1-7 are; provided to create fiat'surfacesjadjoinin'g said fins 11 which" are also flat on their ends adjoining said failings 17 (FIGURE 3); 1 7 Referring new s FIGURE 2, where a'body structure is indicated in general by"18, a tail irotor for countering torque of said rotors 1 3is indicated at 19,20 indicates 1 forward landing'gear; zllindicates rear landing gear and". 23 indicates arotor control'shousing'; vCyclic feather, of saidr-finsr-llis broughtaabout bythe pilot when he-{rnoves f .his directional controlgs'tickZS in the'direction he wishes to travel. When hovering orin'vertical ascent 'ordeiscent,

thepilots directional controlstick 25 is heldin a neilt'r'al a position, thus allowing no cyclicjfea'ther of 'said fins 11i Mechanisms well known to those skilled inrthe art will befsuitable to link saidpilotsdirectional control 's tick t o the fin lateralcy clicfeather; lower torque tubet27, and to :mechanism" allows said cyclic plate assembly to travel I an arc aboutfthe points of attachment of rods 61ttotl1e' jack screw beam 59; when fin collective feather, is changed itiisnot necessary to incorporate compensating linkage, I because the, rods fcanflbe long eno u' gh to n1ake the;radius of the whichfthe cyclic plategassernbly travels large enoughfsojthatthej cyclic plate asscmbly isvmoved oiflcenter only." ,anginsignificantamount when collective feathersof the finsiszchanged; This causes relatively little fore and aft cyclic feather elfeets'of fins which may be cancelled out by a slightmovement'of the pilots' directionalucontrolf'stick if the fore andaft'cyclic feather effects should not be wantedfl a Said cyclic .coritrol plateassembly 3 9 'consisting jof' secure said cyclic control plate assembly 39 to said cyclic control universal assembly 83. v

Torque is transmitted from cyclic control universal assembly 83 to said ring65 by the torque springs 95 and 97 which are attached to the spring pins 99. on said cyclic control universal assembly and spring pins 75 which are 1 attached to bearing'retainer plate 73. --The outer race of said bearing 71 and the retainer plate turns with ring of l.- shaped plates 117, between which are said yokes 89,v

each of which houses said bearing 87. Bearings 119 are in said plates 117 to' provide pivotal mountings for said yokes 89. Bolts 121, extending through bridges 1 23,- spacers 125 and said plates 1 17, hold said bell crankassemblies 91 together. Said bridges'123 are of hard material and are polished in the area of contact with said torque springs 95 and 97 to resist wear from the slight pivoting action of the said An integral said lower fin 11.

action is transformed by said cables 159, through conne'ctionof said cables to fin-structural'members 162 (FIG- URE 3), to 'a back and forth pivot, or cyclic feather I v movement, of said fins 11. Identical upperand lower spindles 163 (FIGURE 3) which are bolted to'getherby bolts164 provide pivotal-attachment of said fins 11 to rotor blade spars 165 without obstructing openingthrough said spars165. j Bearings .166 and. 167 are provided on" said upper and lower spindles 163 to reduce friction as said fins 11 pivot back and forth on said spindles. Said structural members 162 extend from upper end of said upper fin 11 downward through. said fairings 17 said rotor blade 13' and terminate at the lower end of 162 to move back; and forth as said fins 11 change angle of incidence. 5 p

Though fin cyclic feather and fin collective -feather may be actuated either sepanately or simultaneously, .it

should beunderstood that fin cyclic featherprincipally effects horizontal -movemen-t ofthe aircraft, and fin) collective feather principally effects the lift of the air-.

craft whether "separately or simultaneously actuated.

Collectivefeather of said fins 11. is brought about by the pilot when he movesfthe fin collective feather. con- I trol lever167 (FIGURE 2) to select the desired amount torque-springs whenfi'n cyclic feather control is applied. Torquefrom said'rotor shaft 41 is transmitted to cyclic I control universal assembly 83 by contact of internally splined ring 105 with the splined sleeve 127 which is fitted between said rotor shaft 41 and the lowerend .ofthe rotor hub mast 129 and is held in position by bolts 131.

When'fin cyclic feather control is actuated, the offcenter movement of said cyclic control plate assembly 39, causes said bell crank assemblies 91, to pivot at 133 (FIGURE 6) and pushrods 135 up on the side in the direction of movement off-center of cyclic control plate assembly 39and to pull rods 135 down on the opposite side.

'-Therefore, as said cyclic control universal assembly:

83 (to which rods 135 are attached). rotates, a vertical push-pull action is transmitted by said rods 135 to fthQ (FIGURE 5), located in said rotor hub 15. Said bell cranks 137, are pivotally attached to fittings 139 by bolts 141, and saidfittings are attached to said rotor' hub mast' 129 by bolts 143 that also attach said rotor hub to said' rotor shaft 4-1. Inserts 145 (FIGURE '6) provide seat's for-heads of said bolts 143 and 131 and distribute stress loads. A back and forth movement, approximately in line with the pivot axis of the rotor bladetorque arms 147 (FIGURE 5) is transmitted by the upper ends of the ver-' 11 in a manner to cause leading edge of said to pivot outward when control lever 167 is moved aft' and to 7 offin pivot-out or pivot-in with respect to leading edge of fin 11. Said control lever 167 is linked to said'fins' pivot inward when said control lever is moved forward.

Conventional means well known to those skilled in the art will be suitably employed to causemovement of said control lever to actuate jack screw/168 by connec? tion' of cable 169 (FIGURE 3) to move said push-pull rod 47 up or down, thus providing the necessary actua tion of the mechanisms relating to the collective feather control of said fins 11." The antitorque scissor 170 is employedto prevent torquing of said rods 47 and 45.

The up and down movement of said rod .47 istransmitted to the lever 171 by pivotal connection to said lever;

Said lever pivots about the center-line of bolt 173,that outerendsof' the horizontal legs of the bell cranks 137 attaches said lever1'71 to the body structure, and raises or lowers said cyclic control universal assembly 83 by piv otal connection of links 175 to studs that are integral a with yoke'177. .Said yoke 177 attaches to the outer tical legs of said bell cranks 137, to levers 149 by links 151 (FIGURE4). Said levers pivot at theinpointsofi i attachment by bolts 154 to horns 153 (which extend from said torque arms 147, opposite to the direction of rotation of said rotor hub), as theiropposite ends move back and forth approximately in line with the pivot axis of are pivotally attached to saidlevers 149 betweenpoints of attachment of said levers "14910 said links 151 and to said horns 153 and extend 'outwardly parallel to said said rotor-blade torque arms 147. Push-pullrods15S I torque arms 147 through elongated holesinsaid horns to wardfrom' the'sleeves "160,which are integral parts of said horns 153, are studs 161.that provide pivotal attachments forsaid cross beams157.

The back and forth action of said bell cranks 137 is transmitted by said links 151, to said levers149, and from said levers a see-saw action is transmitted tov said cross beams 157 by said push-pull rods 155 and the'isee-saw race of said bearing 179 as the inner race o'f said bearing turns with said cyclic; control universal, assembly 83. Y By pivotal connection of said rods to said-bell crank assembliesg91; thefraising ,or loweringbf cyclic control universal assembly 83- causes the'u'pper endsof said' bell cranks 137 to tr'ansrnit movement inward toward the axis of rotation of said rotor shaft or outward to? ward' said fins 11, thus. changing angle of "incidence .of

said; this by unified linkage of said links 151 (P1654);

said levers'149, said rods and said beams 157 lflojrcing said beams to pivot about said studs 5 161;; and effect collective feather of said fins'1' 1 by connection of 1 said structural members, 162 in: said said cables 159;,to

fins 11. 5 d e Though the pr-incipal Collective pitch of said rotor bliades 13;is,controlled'l by't'he pilot. as he selects the desired degree of pitch of I Slots in said fairings 17 and said blades 13 provide clearance for said structural members function of said rotor bladesis to provide lift of the aircraft, they-also serve as arms. for

mountingsaidfinslh Collective pitch changing of; said rotor ,blades 13 may be accomplished without changing setting of collective feather or cyclic feather. of said fins yoke.

angles of attack, of said rotor blades increases inran ,attitude' to create lift when saidJQtQ'r'bIade ,collectivepitch i control stick 189 ismoved aft, audjlrwh'en said rotor blade collective pitch control sticklis moved forward,-thevangles said rotor blades, by movingjthe' rotor; bladeicollective' pitch control stick 189, (F1GURE,2).-;.The,p itch;; or V downward of rotor blades whileiproviding v cushioned rests for said rotor' blades When, the. pins.

' 243jare=pulled from aligned holesin' said fittings; 215 and said links 2319, said links will pivot about the center'.

line of attaching bolts 2145 and hang free, permitting said rotor blades tofold downward pivoting about the centerof attack ofsaid rotor; blades decreases; 1 Conventional means Wiuf tb1SUi.tab1 y ,employed tocause the rod 191' (FIGURE 3) to move' upsor down as necessaryito effect" collectivelpitch of said rotor.,-blades,13 Said rod1191,

being'pivotally attachedto lever 193, forces said v lever to line of said attaching bolts 235. This facilitates removal; attachment, orstowage'of said rotor blades. 1

1 system rotated approximately 90 degrees-"with respect: to

pivot aboutthe center=line of the bolt; 1 95 that attaches said -lever.to :link 197 as it raisescor lowers yoke 199 by pivotal connection to the studslthat' are integral with said Said link 197 is pivotally connectedto'the body structure by belt 201. Said yoke 199 houses the-outer 7 race of the bearing 203 that is secured in said'yoke'and the innerjrace of. said bearing isforced to tnrn wr-th ring 1 205 that-is attached to beam 207. Scissor l-ink ZGS prea 1 vents torquing of said lever1193', Said beam 207 extends Tthrough slots in said rotor shaft-41 and is fixed to the lower end ofrod 209 Said 'rod'209 extendsupward from place ofattachment of said beam; 207, inside said rotor shaft 41, and transmits an up or down movement to the pivotal point of attachment to the spider fitting sleeves 160ftha't are integral parts ofsaid horns 153 are oting about their' lengthwise axes by-bearing21'61 which is subject to radial loading only, and thrustibearin-g 217 1 forward on the aircraft from what.' is referred to as for.- ward in application. Rotation of this controlsys 'tem. 90-degreeswith respect to the aircraft would cause what is referred to here as the'lateral cyclic feather; control to become the fore and aft cyclic feather controland 1 the foreand aft cyclic feather controlrefe'rredto here would become the lateral cyclic featherkcontrol, :r 1 1 T o those-skilled inthe,art,-it will be obviousthat manyvariations and modifications of the: present invention are poss ble in the light of the abovef teachings, thereforel wish'not to be limited'rin this invention tothe specificdetails'herein set forth but wish -toreserve any'yariationa, modifications or mechanicalg equivalents that fall within the scope of the following claim.

1 lclaimz. 1

f A control mechanismforirotary winged aircraft having ,a rotor shaft with rotor blades'mounted thereon',a cylinrdrical central ,trunk member concentric withgand' axially I movable external of the rotor shaft, an externallytsplined -sleeve;conrle cted with the outer surface ofQsaidssha-ft for 1i; transmitting'torque to an internally 'splined ring' com;

I nected with said trunk, apluralityof identical'bel'l-cranks which carries-the centrifugal force load of said rotor blade j tion'edr to exert thrust'inward. "Ihe outer races of said bearings 216 and 217 are fixed relative to said rotor hub 15 and the inner races of said bearings '216 and 217"tnrn back and forth withsaid rotor blade torque arms 147 as collective pitch of the rotor blades changes; Said rotor blade torque arms are attached zbly 15 by nuts 219. H 1 a V The inner bearing housing 221; (FIGURE 4) consists to said rotor hub assem-- 1 13 and said fins 11 whentheyarerotating; plus the thrust .1 f of said fins'when said fins are positioned to pull outward, and minus the thrust of said fins when said fins are posiof identical upper and lower halves." Said innerbearing housings attach to the upper disc 223 and tothe lower disc 225 by the bolts 227; 'Iheouterhousings 229 attach to said npper'dis'cf 223 and near outer diameter of 'cone 231. The inner diameter-of said lower disc 225 1 attaches to the top end of said rotor hub. mast'129. The inner diameter of said cone 231 is joined to the lower'endof said mast 1 29 bysaid-b'olts 131.

Boot 233 attaches to the lower end of said mast 129 J p and to saidring 1 05 tokeep foreign matter from interfer iingrwith-sliding action f said splined sleeve 127 in said internally splin d i r a 1 I I Slots'in the upper endiof said rotor sh aft'41 and jn the lower endof1said mast 12 9, that are provided to-adrnit arrnsfof said spider fitting211, allow: expansion of said i'otor's haft and contraction of said 'mast when said bolts 7 131 and 143 aretightene'd, Thisinsnresa good fitting together of said .rotor'hub 15 and said shaft f40 without close tolerance machining. 'Saidrotor bladesf13 are attached said rotor, :blade torque arms 147'by bolts 235 that arGQalignQd in said fita r tings 215 and fittings 237 to allow pivoting about-the center-line of'said'bolts so that said rotor blades may be folded downward orupward; Said fittings237 are in-' tegral with said spars; The links 239 hook torsaid fittings 237 r (FIGURES) and restrictnupward hinging 'ofi rotor blades 13, and hard rubberdikelstop 241 restricts WEST, Primar yExhrnin et, 7

connected with said trunk to pivot about axesradial of sard trunk, each of gsaidbellcranks being pivotal also aboutaxes perpendicular to "and intersecting said radial axes, one. of the two-=legsof5each'of saidt-bell-cranks extending frompoint of attachment'of said bell-cranks with 1 said trunk parallel'to said trunk and theotherlegr-e ii tending radial of said trunk when said controlling mechai I nrsrn is not-actuated; a plate comprising .a nonrotatable portion concentric with arotata'ble portion which is joined in a univer'sally pivotal manner said'iparallel' legs of said bellcranks, said plate I being concentriewith said .trunkfwhen said contro'lling mechanismis notiactuated and having a circular opening concentric with said trunk and of greater diameter thansaid trunk to permit moving said plate off center for actuation of said controlling"? mechanism; spring-like members spiraling collectively around parallel legs 'of'said bell-cranks frompoints of attachment withsaid trunk to points'of attachment the rotatablefpo'rtionofl said plateto transmit torque 1 Stabilize a mss i m a n utral r io from said trunk to rotatable port-ion of said plate, and to References,Cited by UNITED STATES PATENTS 1 MILToN BUCHLER, Examiner; a

I Itv should be noted here that on certain types of rotary Winged aircraft it will be feasible to install this control 

